Skin - Reference Guides

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The Skin
The Skin
2nd EDITION
• The skin (or integument) is the Figure 1: Layers of the Epidermis (Cross Section) Stratum corneum
• Outermost “horny layer” of thin squamous cells that are continuously shed and
largest organ in the body, and has replaced on the surface • The cytosol of these cells is replaced by
many functions, including water-repelling keratin • Functions as a barrier to water loss and threats
protection, sensation, from the environment
thermoregulation, and some
metabolic processes • Different Stratum lucidum
areas of the body have different • “Clear layer” that is especially prominent in thick skin • Cell nuclei are
generally absent, and the cells are filled with a soft gel-like substance called
functional characteristics, such as eleidin, which eventually becomes keratin
thickness, color, and the presence Stratum granulosum
of epidermal appendages (hair, • “Granular layer” where keratinization begins • Cell nuclei are either absent or
glands, and nails) degenerate • This layer may be absent in thin skin
Stratum spinosum
• Skin is formed by two layers: • “Spiny layer” where protein synthesis occurs for keratin production
the epidermis and the dermis • This layer appears prickly under a microscope
• Most skin is classified as thin, but
skin of the palms and soles of the Stratum basale
• Single “base layer” of columnar cells where mitosis occurs • Cells migrate
feet is classified as thick • In thick from here to the upper layers and are eventually shed • Melanocytes, which are
skin, the epidermis is thickened, but cells that produce the pigment melanin, are found in this layer • Differences in
not the dermis • Skin thickness skin color are due to the amount of melanin produced, not the number of
ranges from 0.5 mm to over 5 mm m elanocytes
Stratum germinativum
• “Growth layer” referring to the stratum spinosum and stratum basale together
M erkel’s discs Nociceptors
• Superficial nerve • Nerve fibers, ending in
endings that detect dendritic knobs, that are Pore Meissner’s corpuscle
lght touch the primary sensory • Superficial, large receptors that respond to light touch and
Figure 2: Cross Section of receptors for pain low-frequency vibration • Found in nipples, lips, and fingertips
Generic Skin Area
Dermal papillae
Epidermis • In thick skin, these are
• Outer, thin layer of arranged in curving
the skin • Consists of parallel ridges which form
layers of stratified fingerprints and footprints
squamous epithelium
• Lacks blood vessels
and has few nerve Arterioles, venules &
endings • Thickness capillaries
varies on the body, • Supply blood to the skin
with thickest areas on • Help regulate body
the soles and palms, temperature by adjusting
and thinnest on the blood flow to radiate excess
eyelids heat • Capillary dilation
causes blushing in face
Dermis Krause’s end bulbs
• Inner, thicker • Smaller variant of
connective tissue layer Meissner’s corpuscle with
mostly of collagenosed fewer endings, detecting
fibers, with some elastin touch, vibration, and cold
and reticular fibers • Often found in mucous
• Contains specialized membranes
structures such as hair
follicles, sweat and
sebaceous glands, blood gland (sudoriferous)
vessels, nerves, and • The most numerous type
lymphatic vessels of skin gland • There are
two types: eccrine
(merocrine) and apocrine
Pacinian corpuscle • Eccrine sweat glands
• Nerve receptors found are the most important,
in deep skin that respond producing transparent,
to deep pressure watery perspiration all
• Mainly found in the over the body which
hands and feet lowers body temperature
and eliminates waste
Subcutaneous layer • Apocrine sweat glands
(hypodermis) become functional at
• Connective tissue layer puberty, and produce a
below the skin containing milky, odorous secretion in
a large amount of fat the axillary and genital
• Carries the major blood regions
vessels and nerves to the
overlying skin